1. Field of the Invention
The present invention relates generally to a multi-band antenna, and more particularly to a multi-band antenna used for wireless local area network.
2. Description of the Prior Art
As communication technology is increasingly improved, the weight, volume, cost, performance, and complexity of a communication system also become more important, so antennas that transmit and receive signals in a wireless communication system especially ‘draw designers’ attention. In a wireless local area network (WLAN), because the space for setting up an antenna is limited and the antenna should transmit a large amount of data, the antenna should be carefully designed. And for the requirement of small size, the antenna is needed to be able to transmit all signals of WLAN bands, 802.11b(2.4 GHz) and 802.11a(5.2 GHz).
Referring now to FIG. 1, a multi-band antenna 1′ is shown and includes a radiating element 2′, a grounding element 4′, a feeding line 5′ and a connecting element 3′. The radiating element 2′ comprises a first radiating portion 2a′ and a second radiating portion 2b′. The first radiating portion 2a′ comprises a first radiating arm 20′, a second radiating arm 21′ and a third radiating arm 22′. The second radiating portion 2b′ comprises the second radiating arm 2′, the third radiating arm 22′ and a forth radiating arm 23′. The first radiating arm 20′, the second radiating arm 21′, the third radiating arm 22′, the grounding element 4′, the connecting element 3′ and the feeding line 5′ compose of a first inverted-F antenna. The second radiating arm 21′, the third radiating arm 22′, the forth radiating arm 23′, the grounding element 4′, the connecting element 3′ and the feeding line 5′ compose of a second inverted-F antenna. The first inverted-F antenna is operated at a lower frequency, and the second inverted-F antenna is operated at a higher frequency. However, blind area unavoidably exists in the multi-band antenna 1′ which influences performances of the multi-band antenna 1′ in great extent.
Hence, an improved antenna is desired to overcome the above-mentioned shortcomings of the existing antennas.